As you know, Google said they will be expanding AMP beyond news stories but also into all types of pages. But they did not give a timeline.
Recently some folks have been saying they've been seeing the AMP logo and AMP results in the main mobile Google search results, outside of the top news carousel.
So Glenn Gabe asked Google's Gary Illyes about it and Gary said that Google may be testing it in the wild. Here is the set of tweets:
Google is always testing stuff, so testing AMP outside of the AMP demo site and in the wild shouldn't surprise anyone.
Forum discussion at Twitter.